Make sure you have installed the extension titletips!

Import from online repository and install t3xtooltip.

Add the extension-template from titletips and make sure that its not beeing cleared out later (PAGE-object!).

Add the extension-template from t3xtooltip to your template (AFTER css_styled_content and any other extension which takes control over styles.content.get*, because t3xtooltip uses the postUserFunc).

Create a new page (sysfolder).

Insert a new record: “Tooltip Definitions”.

Set constants “plugin.tx_t3xtooltip_pi1.PIDtooltip” to the PID of the sysfolder which contains your tooltip definitions (see TypoScript below).

If you want to style your tooltips with CSS, take a look at the typoscript of titletips.